Many manufacturing processes involve high-temperature process steps. One example is the solder-reflow process used in the manufacture of circuit boards. In the solder-reflow process, circuit boards are passed through an oven on a conveyor. Within the oven, the circuit boards are subjected to multiple zones at varying temperatures. With the advent of no-lead solder, the temperatures used in solder-reflow processes have increased. Too much heat, however, can damage the circuit boards. The ovens must heat the circuit boards enough to fuse the solder, but not enough to damage to the circuit boards.
Solder-reflow processes are just some of the many high-temperature processes that require careful monitoring. Temperature is usually the key environmental parameter, but some processes also are sensitive to other parameters, such as relative humidity. Environmental parameters such as temperature and relative humidity can be monitored with electronic devices, which typically have at least one sensor and associated circuitry, including one or more components such as a processor, a memory, a DC power source, etc. These electronic devices are typically passed into the process environments and experience the same conditions as the product being processed, which may occur over several minutes. The recorded data can be monitored real-time or reviewed after the process is completed. In this way, the profile of the process can be studied and optimized. For example, the temperature profile of a solder-reflow process can be maintained within the optimal processing window.
Certain components of electronic devices, e.g. batteries, are damaged or degraded when exposed to high temperatures. Thus, some conventional approaches to data-gathering use insulation around the devices in an effort to shield the devices from the full effects of the high-temperature environments. For example, U.S. Pat. No. 6,402,372 discloses a flight-data recorder surrounded by a housing comprising a high-temperature, insulating, structural material, such as a fiber-reinforced epoxy. Such an approach is typically not feasible for production-oriented monitoring devices, however, at least because of size considerations, cost considerations, and the need to have ready access to the devices.
As typical process temperatures increase, the conventional approaches to insulating electronic devices prove to be inadequate. A need exists for providing increased thermal protection to electronic devices that is relatively inexpensive, durable, and able to work within the physical and environmental constraints of conventional ovens.